Phosphate sorption and leaching in a sandy loam soil amended with biochars: Evidence from batch and column experiments

Articles in Press

Document Type : Research Paper

Authors

Department of soil science, Collage of Agriculture, University of Kurdistan, Sanandaj, Iran

10.22059/ijswr.2025.400939.669998

Abstract

One of the modern approaches to improving soil properties is the use of biochar. However, previous studies have reported inconsistent findings regarding its influence on phosphorus (P) dynamics in soils. Given the critical role of P availability in plant nutrition, a deeper understanding of the phosphate sorption and release in the presence of biochar is essential. This study aimed to investigate the sorption and release behavior of phosphate in a sandy loam soil amended with different types of biochar. Two laboratory experiments were conducted: the batch sorption tests to evaluate the phosphate adsorption capacity of biochars, and the soil column experiments to assess their effects on phosphate movement and leaching. Biochars were produced from two regionally common biomass feedstocks, winter wheat straw (Triticum aestivum) (WS) and pruned apple tree branches (Malus domestica) (AW), each pyrolyzed at two temperatures (300 °C and 550 °C). Batch sorption tests revealed that raising pyrolysis temperature from 300 °C to 550 °C reduced phosphate sorption capacity (from 1.98% to 0.58% for AW biochar and from 5.57% to –1.12% for WS biochar), with wheat straw biochar produced at 550 °C even exhibiting phosphate release. The findings of the batch experiments were consistent with those from the soil column experiments, in which biochars with higher phosphate sorption capacity in batch tests also exhibited lower phosphate leaching in the soil columns. The findings of this study highlight that both the biomass feedstock type and the pyrolysis temperature are key factors in determining the biochar’s ability to sorb or

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 15 December 2025

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